Adjective-
1. Belonging to an exclusive group (clique) made up of people wearing Dr Scholls Gel inserts.
2. Having greater perceived social value due to inclusion in, or relation to, said group.

This term is often used in conjunction with other words that rhyme with it. The more rhyming words used, the more one is Gellin'. Misguided individuals who believe that they are Gellin' when they are not often say that they are "gelling." It is easy to pick out these individuals because they never rhyme their words. And they are horrible dancers.

A: Are you Gellin'?
B: I'm Gellin' like a felon. Care for some melon?
A: I'm so Gellin', I'm Gellin' like Magellan.
C: I'm gelling!

adj: In the state of mind where getting the news that your dog was hacksawed to death by a hipster wouldn't bother you one bit. Only obtained by wearing Dr. Scholl's gel shoe insoles. The care-free attitude has been described as relaxing on a hammock made of hemp, while in a coma.

v: being in the above state of mind

Now, here are some words that are more likely to be spoken while gellin'. With these words can come great rap lyrics. And that's sayin' somethin', yo.